Recreational vehicles often require roof-mounted ventilators for the ventilation of various appliances and a wide variety of vents have been used for the venting of the vehicle interior space, stoves, sanitary systems, exhaust fans and gas refrigerators. The most commonly employed vents are of a sheet metal construction which are of a bulky assembly and difficult to ship, clean and maintain. Also many of the vents presently available have greater vertical dimension than desired and are not capable of providing the venting capacity necessary.
A roof-mounted vent formed of a nonmetallic, synthetic plastic material of a molded construction, as disclosed in U.S. Pat. No. 3,654,850 has been marketed for recreational vehicle use and this construction has the advantage of relatively low cost, low profile and, as the parts are nestable for shipping purposes, freight costs are minimized as compared with one-piece metal vents. However, vents constructed in accord with U.S. Pat. No. 3,654,850 support the cover upon the base upon elongated tabs wherein vibration may occur between the cover and base members, but the greatest deficiency of this construction is the necessity to attach a screen to the base to prevent the entry of leaves, birds and other foreign matter into the vent. In the patented vent the screen must be separately installed in the base by a stapling operation, or the screen is placed upon the recreational vehicle roof and the vent mounted thereon. In either case, the installation of the screen constitutes a separate installation operation, is often improperly accomplished if installed by inexperienced personnel and significantly increases the cost of the complete vent assembly.